The invention is directed to a mattress tub which forms the upper support portion of a mattress and can as well form a lower support portion which essentially becomes uppermost when the mattress is turned or flipped in the customary fashion. The construction of the mattress tub directly affects the comfort and "feel" of the mattress because it is the support portion upon which a sleeper or patient rests and is thereby supported.
Upper support portions of the type described are relatively common, as is reflected by the disclosure of U.S. Pat. No. 5,317,768 in the name of Alvin R. Klancnik granted on Jun. 7, 1994. This patent discloses a mattress which is formed by a coil spring structure, a bottom cloth layer thereabove, next a convoluted foam layer having upwardly directed peaks and upwardly opening valleys, and spanning and covering all the latter are an upper fiber layer and an outermost cloth layer with all of the components, excluding the coil spring structure, being held together by stitching. The patent recognizes inherent problems in a mattress of this type, such as the crushing of the fiber material which causes a loss in resilience and prevents the same from returning to its original position even after weight has been removed. Another disadvantage of the mattress is said to be the retention of moisture by the top surface should a sleeper perspire. Once wet, the fiber is slow to dry and the retained moisture is said to result in an unpleasant aroma. The problem of such mattresses is resolved by the patent disclosure through the utilization of the convoluted foam layer, located beneath the fiber layer, having upwardly directed peaks which are partially compressed when weight (a person or sleeper) is applied thereto and which return to their no-load position once weight is removed. This is said to move or exercise the fiber layer thereby reducing matting and also forces air movement which dries any moisture from the fiber layer. The convoluted foam layer in the top surface also increases the comfort or softness of the mattress since the peaks are quick to respond to a weight by compressing.